Grinding mills



A. F. MEYER GRINDING MILLS May 6, 1969 Filed Feb. 9, 1967 INVENTOR ATTORNEYS United States Patent US. Cl. 241-82 4 Claims ABSTRACT OF THE DISCLOSURE A grinding mill having a chimney projecting upwardly from above a hammer grinder, wherein those opposing walls of the chimney which are in planes transverse to the axis of the mill converge toward one another in an upward direction. Thus material projected into the chimney by the grinder will fall back onto intermediate portions of the mill rather than onto the ends thereof to produce more uniform wear on the hammers. The other two opposing walls of the chimney are diverging in an upward direction to prevent reduction in outlet capacity because of the convergence of the first mentioned walls.

BACKGROUND OF THE INVENTION Field of the invention! The present invention pertains to a hammer grinder of the type which projects some of the material upwardly into a chimney, and in which the chimney has an upperend return bend for the discharge of non-grindable materials, the invention being particularly useful in the grinding of household refuse to render disposal thereof more etficient.

Description of the prior art In prior art such as the Gondard Patent No. 3,082,963 there is a parallelepipedic chimney. In this type of construction it has been found that the material being ground works toward the ends of the hammer mill casing with the result that the end hammers get excessive Wear. The more the end hammers wear down the more accentuated the condition becomes, and the greater the concentration of material in the corners of the hammer mill casing. This eventually results in less grinding of the material in such corners, with the result that the output of the mill is so reduced that there is less ground material passing through the grates. Wear on the end hammers also reduces the throwing elfect of said end hammers on nongrindable material so that such material is not rejected as it should be.

SUMMARY OF THE INVENTION The present invention provides a grinding mill having a chimney of novel and changing cross-sectional shape so arranged as to cause recirculated material to fall back on intermediate portions of the length of the hammer mill rather than on end portions thereof, to reduce excessive concentration of material on the end hammers and provide for uniform distribution throughout the length of the rotor whereby substantially uniform wear on the hammers throughout the axial length of the hammer mill is obtained.

It is therefore a general object of the invention to provide a grinding mill in which the hammers wear uniformly.

A further object of the invention is to provide a hammer mill having a high output of ground material passing through the grates.

A further object of the invention is to provide a grinding mill of the type having a chimney with provision for the discharge of non-grindable materials, wherein said discharge is rendered more eliicient and complete.

3,442,458 Patented May 6, 1969 BRIEF DESCRIPTION OF THE DRAWING In the drawing, illustrating one complete embodiment of a preferred form of the invention, wherein the same reference numerals designate the same or similar parts in all of the views:

FIG. 1 is a side elevational view of the improved grinding mill, a lower portion being broken away and shown in vertical section; and

FIG. 2 is a view looking at right angles to FIG. 1, taken generally along the line 22 of FIG. 1.

DESCRIPTION OF THE EMBODIMENT Referring now more particularly to the drawing, the numeral 10 designates a floor or platform having an opening 11 therein for the passage of ground material. Below the floor or platform is a suitable endless conveyor 12 having a hopper-like receiving opening 13 positioned directly below the opening 11 in the platform 10. The endless conveyor includes an endless belt 14for carrying away the ground products.

Mounted on the platform 10 is a hammer mill 15 having an outer casing which is rectangular in horizontal section and formed of parallel end walls 16 and opposing side walls 16'. A motor 17 drives the hammer mill shaft 18. The latter carries rigidly mounted discs 19 between which hammers 20 are swingably mounted, as is well known in the art. At the bottom of the hammer mill is a curved grate 21 through which ground material is adapted to pass before it falls through the discharge opening 11. The top of the hammer mill casing is entirely open as at 9 for the full length and diameter of the rotor.

Projecting upwardly from the opening 9 of the hammer mill is a chimney 22 having a top return bend portion 23 for receiving rejectable material which passes over the top 24 of wall 25. The return bend 23 discharges into a suitable chute 26 which may lead to a receptacle or vehicle.

Referring now to FIG. 1, it has heretofore been conventional to have the chimney walls which correspond to the walls 25 and 27 parallel to one another. With the present invention the walls 25 and 27, which are those walls which extend upwardly from the end Walls 16 of the hammer mill and which are in planes extending transversely of the axis of the hammer mill, converge upwardly toward the center line C, as is clear from FIG. 1. It is also conventional to have the other two walls straight and parallel. With the present invention, however, the walls 28 and 29 diverge upwardly, as illustrated in FIG. 2, away from center line C. It is preferred that the divergence of the walls 28 and 29 be such as to approximately compensate for the loss of area due to the convergence of the walls 25 and 27 so as to maintain a substantially equal cross-sectional area all the way up to 24. Whether or not the exact cross-sectional area is maintained is not critical. Furthermore, it may even be advantageous to increase the cross-sectional area by having the walls 28 and 29 with still greater divergence upwardly.

The amount of convergence of the walls 25 and 27 is such, depending upon the particular type of material being ground, as to obtain the maximum uniformity of distribution axially of the rotor as the material falls back down. By having such convergence, material is caused to fall back into the hammer mill intermediate its length and excessive concentration of material near the ends is eliminated. Thus more uniform wear on the hammers results. The height of the chimney may be varied somewhat depending upon the nature of the materials being handled. For ordinary household refuse the chimney height should be about fifteen times the diameter of the rotor. If the chimney is too low, materials will be rejected which should not be, and if the chimney is too high, there will be incomplete discharge of the rejectable materials.

Material to be acted on may be fed into the mill from a conveyor 31, which discharges into a hopper 32 communicating with an inlet opening 33.

OPERATION During normal operation of the hammer mill, which mill is particularly useful in the handling of refuse, the mill is rotated at about 1200 rpm. for refuse. The nonrejectable material is propelled upwardly into the chimney 22 and then falls downwardly a number of times before it is ground fine enough to pass through the grating 21. The rejectable materials, usually metal or plastic containers in household refuse, are bounced up and down in the chimney 22 until they are propelled high enough to hit the top 30 of the chimney. Due to the angle of this top they are then directed, as indicated by the arrows at A, down through the return bend portion 23 and into the chute 26.

By use of the present invention, with the chimney of the unusual cross-sectional shape, all non-rejected materials which fall back onto the rotor fall onto intermediate portions thereof because of the upward convergence of the walls 25-27. Thus there is more uniform wear on the rotor and the customary excessive accumulation on the end hammers is eliminated. This prevents the customary excessive wear on the end hammers which so reduces the efficiency of a mill of this type.

In the handling of household refuse the non-rejectable materials are eventually all ground up by the hammer mill to a fine enough degree to pass through the grating 21, and this includes glass from glass bottles. The purpose of grinding household refuse is to make the disposal thereof easier and more efiicient. The ground material from the conveyor 14 is usually taken to a land fill. Because the refuse is uniformly reduced in size it will pack compactly into the available space in the dumping ground. The rejected material from the chute 26 is quite often also dumped on the land fill and then covered over with the ground material. This rejected material has also been substantially reduced in volume because of the battering from the hammers of the hammer mill.

In cases where it is desired to burn the ground material, this can be done very etficiently because the material is uniform in size and because the principal non-combustibles have been removed. Thus this incineration can be performed in a less expensive type of incinerator.

When the ground material is to be deposited in a dump, it packs so closely that undesired combustion is practically non-existent. Thus the usual smoke nuisance and fire hazard from this type of dump is eliminated.

Various changes and modifications may be made without departing from the spirit of the invention, and all such changes are contemplated as may come within the scope of the claims.

What I claim is:

1. In a grinding mill having a hammer grinder with a rotor rotatable on a horizontal axis, there being a casing for said rotor having oppositely-disposed end walls which extend transversely of the axis of the rotor and having oppositely-disposed side walls and having an open top, a chimney having means for discharging rejectable material positioned with its lower end communicating with said open top to receive upwardly-projected material from the grinder, wherein the improvement comprises providing the chimney with oppositely-disposed wall portions which extend transversely of the axis of the rotor and which are in converging relationship in an upward direction so that material projected upwardly into the chimney will fall back onto intermediate portions of the length of the hammer grinder, the angle of convergence being such as to provide for relatively even distribution of material throughout the length of the rotor to eliminate excessive concentration at the ends thereof, two other opposite wall portions of the chimney extending upwardly in diverging relationship upwardly.

2. A grinding mill as set forth in claim 1 in which the wall portions which are in converging relationship extend upwardly from the end walls of the rotor casing, and in which the wall portions which are in diverging relationship extend upwardly from the side walls of the rotor casing.

3. A grinding mill as set forth in claim 1 in which the hammer grinder casing is rectangular and in which the chimney is rectangular in horizontal section.

4. A grinding mill as set forth in claim 1 in which the angle of divergence of the diverging walls of the chimney is such as to at least maintain a substantially equal crosssectional area throughout the major portion of the height of the chimney.

References Cited UNITED STATES PATENTS 2,692,088 10/1954 Layberger 241-189 X 3,151,814 10/1964 Morgan 24ll86 X FOREIGN PATENTS 425,271 3/1935 Great Britain.

ROBERT C. RIORDON, Primary Examiner.

J. F. MCKEOWN, Assistant Examiner.

U.S. Cl. X.R. 241--189 

